Somsak said the 36 rice mills took part in the scheme in 2002 and 2003 but a recent stock check had found that the rice kept at their warehouses was too old to have been harvested in those years.

Under the programme, mills can buy rice from farmers and seek reimbursement from the government.

The Agriculture Ministry also discovered that premium-grade rice had disappeared from warehouses participating in the rice-pledging schemes. Apart from privately owned mills, two state firms - the Marketing Organisation for Farmers (MOF) and the Public Warehouse Organisation (PWO) - take part in the programme by buying rice from farmers for export.
However, the latest checks found the rice was not of the quality that the millers and MOF and PWO warehouses had declared when claiming money from the government, raising suspicion of foul play.

The government suspects the warehouse officials and millers either swapped high-grade rice for low-grade varieties or had bought old or poor-quality rice from the beginning and made false claims for reimbursement.

Somsak said he had assigned Jira Pimollikhit, an inspector-general at the Agriculture Ministry, to file complaints with police against the 36 rice mills and then it would be up to police to investigate the nature of the cheating.

The minister said subsequent investigations would expose those government officials who took part in the cheating.

Somsak said the checks, carried out by a special government committee headed by Chakan Saenraksawong, director-general of the Agriculture Department, found the quality of rice in warehouses of 16 other provinces was correct.

Meanwhile, a government source said a fact-finding investigation into suspected corruption by MOF officials in Phichit, Chon Buri, Pathum Thani and Bangkok would be completed this week.

The source said Owart Apibalpuwanart, former acting MOF governor, could face severe disciplinary investigation and legal action as a result of the probe.